Forecasting agrobiological properties of wheat straw with different additives--multiple regression models including chemical parameters
1995
Blanco, M.J. | Almendros, G.
The agrobiological properties of 37 composts prepared from wheat straw with a series of organic or mineral additives have been determined through standard chemical analyses and greenhouse experiments with soils of different carbonate content and in the presence, or absence of mineral fertilization. Plant yield on soils treated with the composts was studied in successive stages of development of rye grass (Lolium rigidum), showing significant differences that paralleled the values of a limited number of compost parameters. Under greenhouse conditions and in the presence of mineral supply, the least matured composts led to improved plant yield only in the early harvests, decreasing thereafter which points to a behavior typical for the microbial immobilization of the additional nutrients. The germination (phytotoxicity) index was found poorly correlated with the yield in the different soils, whereas the N and lignin contents provided the most significant information, the results suggesting no cause-to-effect relationship in such correlations. The multiple regression models showed significant differences as regards the system studied when the limiting influence of nitrogen (N) was reduced through additional fertilization. The most significant coefficients for the plant yield were those reflecting the total mineralization rates of the compost, the composition of the water-soluble fraction, and the concentration of lipids whereas, when no mineral solution was added, the yield was explained mainly by the N content in compost and in water-soluble products. In successive harvests, the significance level of the compost N level tended to increase, whereas that of lipid decreased, the former factor showing the greatest influence when carbonates are present in the soil.
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